18.3 Object Generators

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18.3 Object Generators

We have seen how to build individual counter objects, one at a time. It is equally easy to write a counter generator—a function that creates and returns a new counter every time it is called.

   newCounter =     λ_:Unit. let x = ref 1 in                 {get = λ_:Unit. !x,                  inc = λ_:Unit. x:=succ(!x)}; ▸ newCounter : Unit → Counter 

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